Illuminating a fiber with a laser source has enabled the size of the Internet to grow at tremendous speeds by providing for a very quick, high bandwidth, medium for communication. The basic building blocks behind the fiber optic internet are optical components, many of which use lenses, filters and various wavelength multiplexer and optomechanical components for their operation, some of which are waveguide based.
For a device to be useable in an optical communication system at some point at least one fiber, usually an input fiber, must be attached to an optical component. During the assembly of these devices at some point the light coming into the device from an optical fiber must be aligned to the optics block; and the light coming out must be aligned to an output fiber, or in the case of a multi-port device, output fibers. Typically, an input light source is used to illuminate a two-port transmissive optical component, such as a lens through a first input fiber. A detector is coupled for providing a feedback indicative of the optical insertion loss of the two-port device.
Actively aligning during assembly requires a positioning mechanism for positioning of the fibers relative to the optics block. This mechanism typically allows for translational motion of the fibers in three orthogonal directions. For each orthogonal axis, translating that axis results in the optical power changing as that axis is moved. An axis is optimally aligned when during translation the positioner is stopped at the point of maximum power. Upon optimizing of a single axis the procedure is repeated for all the other axes, until such a point is reached where altering the position of any axis in any direction results in the optical insertion loss to increase. Typically, this is done by a human operator actuating knobs to move the fibres.
Conventional means of assembling these optical components consists of using sub micron mechanical 3 axis translational positioners. Typically the Z-axis determines the focusing of the optical system where the X and Y directions are moved to ensure capturing of all the light and aligning the input to the optical block of the device. Optionally a 5 or 6 axis positioning mechanisms may also be used, where the three spherical added degrees of freedom add to further optimize optical parameters. Using more than 3-axis positioners however, leads to a progressively more complicated method of aligning the optical components.
Manually moving each of these axes independently in even a dual multi-axis positioner optical set-up results in a very slow method of aligning the input and the output ports in order to minimize the optical insertion loss. A possible improvement is to automate the positioning of some axes by using motorized positioners and a controller circuit with some form of feedback; for instance from a photodiode. A method which comprises: programming the controller to actuate the actuator of a single axis, while sampling the optical power and stopping translation upon reaching a maximum, then moving on to the next axis and repeating the same method for all other components.
Conventional multi axis positioners used in optical alignment set-ups are made of metal, have tight springs, slow motors and are quite bulky. Automating of these positioners with an actuating mechanism and using a control process result in optimal optical alignment, however the time required for achieving this is quite slow.
A conventional method used by a controller for controlling the positioning of an actuator for positioning of an optical component comprises: moving the optical component by a predetermined increment, sampling the optical power after each incremental, and using a decision process to determine whether the current position is desirable or whether to keep moving the component. Once the position of the optical component in this axis is desirable, the method is initiated on a subsequent axis. In the case where there are many optical components requiring optical alignment in the system, the process of making a decision at each increment leads to a very long time for obtaining desirable alignment. It is more advantageous to use a technique where multi-axis processes are run in parallel.
In many cases it is quite tedious to align a multi-axis multi-component optical set-up. Some complicated systems, for instance those used in holography set-ups, have a large number of multi-axis optical component positioning mechanisms. Where tweaking of each axis on each optical component positioning mechanisms is required to obtain desired optical propagation loss through the optical set-up.
Typically active optical alignment for an optical set-up uses sequential positioning of optical components axes. This results in the optimization of only one axis at a time, where in a complicated system with many components, multi axes optimization requires a long period of time. The controllers, actuators and optical component positioning stages are also expensive because of their high precision. Using an improved method of controlling optical component positions results in the ability to use less expensive actuator mechanisms as well as less expensive optical component positioning stages.
It is therefore an object of this invention to provide an alignment system, for controlling the alignment of components to an optical signal, such that there is a large timesaving realized over prior alignment methods through the use of parallel and sequential alignment capabilities of neural network controller.